English Translation
Count me in.
Would this sentence have a similar connotation as それに私も仲間に入れて ?
This sentence is grammatically broken and sounds unnatural. You need to drop either それに or 仲間に.
私も仲間に入れて。or 仲間に加えて。
仲間 means “close friend” or “comrade”. So, 仲間に入れて means “I want to be part of the inner circle”. It sounds more serious than “count me in.”